The Swear Jar
by TrickPhotography
Summary: This is not what Steve thought he would get for a present on his 100th birthday OR an accidental child acquisition, time travel wonk story about Steve Rogers and Darcy Lewis (Originally posted on Ao3 July 4, 2018)
1. Chapter 1

Steve held his arms out, looking down at the little girl who had attached herself to his legs.

"Uh…" he said, unsure of what to do.

"Daddy, why are we here? You said we were gonna go to Coney Island!" she said, looking up at him. She couldn't have been more than four years old. Her wide blue eyes were filled with tears, and her bottom lip quivered.

"Tony?" Steve looked at the frazzled man who had brought the little girl to the penthouse party.

"Don't look at me!" Tony snapped, raising his hands defensively. "Blame Foster. This is her mess. She just told me to bring her up here while - "

"Daddy," the girl said, tugging his shirt. "Is it your birthday? Uncle Tony said it was."

"Uncle Tony?" Steve echoed before shaking his head and crouching down to look the girl in the eyes. "What's your name, Sweetheart?"

"Emma Grace Rogers," she replied promptly before flinging herself at him. He tensed but relaxed as her small arms wrapped around his neck and her dark hair floated into his face. "Happy Birthday!"

"Thank you?" Steve said, glancing at Tony over the girl's shoulder. When she pulled away he gave her his best Captain America smile and nodded towards the television. "Want to watch something while the grown ups talk?"

She gave him a put upon sigh and crossed her arms, "Then we'll go Coney Island?"

"Sure," he replied. "What, um, what do you want to watch?"

"Dog Cops!" Emma said promptly. It took only a few minutes to get the girl situated in front of the television, a plate of chips on her lap and a glass of water at her elbow.

Both men moved towards the kitchen where Steve turned on Tony. "Explain. Is this some sort of prank?"

"I've got nothing to do with this, Steve. I swear - I was on my way to drag Bruce out of the labs when Jane grabbed me and told me to watch her."

"Steve, what the hell...o," Bucky said, frowning as he stepped off of the patio and saw Emma. She grinned around a chip.

"Hi Uncle Bucky! Are you gonna go with us to Coney Island?"

"Uncle Bucky?" he raised an eyebrow. "And who the hell would want to go to Coney Island on today of all days?"

The girl scowled, "You said a swear word! You have 'ta put money in the jar! Mommy said so. Tell him, Daddy - tell Uncle Bucky he has to."

Bucky looked over at Steve, who ran a hand down his face and shook his head.

The elevator dinged, and they heard Jane talking as the doors opened. " - what happened, she just showed up!"

"Just because I have a niece doesn't mean I'm good with kids, Jane. I didn't come all the way to Manhattan to babysit when I could be working on a tan at Co - "

"MOMMY!" Emma launched herself off the couch, chips flying everywhere, and charged towards the dark haired woman stepping off to the elevator.

They all stared at the girl who was grinned up at the confused woman. "Uh… come again?"

"Are we going to go to Coney Island now, Mommy? And get hot dogs? Can I get two this year? I promise I'll eat them both!"

"Jane?"

"I...uh…" the scientist said, stepping away from them and back towards the open elevator. "I'm gonna be in the lab."

"Jane," Darcy hissed. "What the hell did you do?"

"Swear word!" Emma shrieked, jumping away from her and pointing an accusatory finger. "Daddy, Mommy has to put money in the swear jar too!"

Darcy's eyes followed the little girl's gaze and landed on Steve freaking Rogers, the man she'd been secretly crushing on for the last few months but had yet to exchange more than 100 words with, who blushed and pinched the bridge of his nose as Tony and Bucky roared with laughter.

"Happy birthday, punk - " Bucky finally managed to say. "'Parently the universe got you a girl and a kid."


	2. Chapter 2

Darcy lay awake, tossing and turning, while Steve slept peacefully beside her. She had to fight the urge to fling her pillow at him.

Today was the day.

Should she tell Emma? Let her know that she was going to see her Aunt Jane remind her that she needed to be very careful around her things?

Her heart jumped into her throat - what if she was already gone? Darcy flung back the covers and ignored Steve's confused 'Wha' as she hurried down the hall to her daughter's room. She'd barely reached their bedroom door by the time Steve was up and following her.

"What's wrong?" he said. "Darce?"

"I just need to check on her - go back to sleep, babe." She heard his soft sigh but he didn't turn back.

In the soft glow of the nightlight, they saw their daughter sprawled like a starfish on her bed, her hair a tangled mess on her pillow as she snored softly. Darcy let out a breath she didn't realize she was holding. "'S okay," Steve said. He wrapped an arm around her waist to pull her back against his chest. "She's still here."

"Fuck. Today's going to really fucking suck, isn't it?" she whispered, tears springing to her eyes.

Steve's exhale ruffled her hair. "Come on, let's go back to bed. I'll bring Emma." Darcy warred with herself for a moment, torn between letting her sleep in peace and her own need to hold her close, before nodding. He stepped around her and tiptoed towards the bed, carefully stepping over dolls and a tea set before cursing under his breath when he stepped a Barbie hair brushes.

Emma stiffened and shook when Steve gently lifted her before going limp, her left arm wrapped around his neck and her head on his shoulder. When he stopped beside her, Darcy gently placed a strand of dark hair behind her ear and smiled as she traced it. Over the last few weeks, Emma's independence streak had grown and she hadn't wanted to cuddle as much; Darcy tried not to take it personally but had missed the closeness with her daughter.

"We'll be in in a minute," Steve said, tilting his head back up the hallway. "Gonna see if she needs to go potty." Smiling, she reached up and cupped his cheek, his beard coarse against her hand.

"My hero - saving me from wet sheets and laundry."

"All in a day's work, Ma'am," he smirked before leaning down to kiss her.

She'd settled back into bed when they entered they came in; Steve gently deposited Emma in the middle before getting in and propping himself up on an elbow to face them. His hand stretching across the bed to rest on the swell of Darcy's hip as his thumb began to absently stroke the skin where her t-shirt had ridden up. "You gonna be okay?" he asked.

"I just… I know she's going to be okay and that she'll have fun at Coney Island, but what if she gets scared? What if something goes wrong this time and Jane can't get her back?"

"That's not going to happen - you know that."

"I know that she disappeared from the lab but we don't know where she turned up. What if - "

"Jane - both of them," he smirked and shook his head. "They wouldn't let that happen. You've been working with her to make sure Emma gets back in one piece."

"It's theoretical work, Steve!" Darcy hissed. "We can't test it and what if - "

"It's going to work."

OOO

For all of the forewarning they had, Emma Grace Rogers came as a surprise.

Only eight months after meeting again, Darcy found herself sitting in the bathroom with her back against the wall - literally and figuratively - with a positive pregnancy test in hand, the result of her inability to schedule an appointment to get her IUD replaced around her and Jane's busy travel schedule coupled with Steve surprising her with a weekend away from everyone and an unknown tear in the condom.

In addition to the newness of their relationship, the timing wasn't ideal. She and Steve were still trying to figure out how to balance their crazy schedules - with Jane's Nobel nomination, she was frequently asked to visit observatories and other labs where she dragged Darcy along as her personal assistant/manager. Steve… well, he was busy saving the world. The few times they had been in the same physical location it had been great, but relationships weren't sustained by phone calls and texts alone.

And this was definitely news to deliver in person.

Darcy slept fitfully for the rest of the night. She made sure she was always touching Emma, who drool as she sprawled across her father's chest, fingers buried in his beard.

When it was finally light enough to justify getting out of bed, Darce slid out from between the covers and had to take a few deep breaths as she gripped the mattress. She heard Steve's sharp inhale before his hand groped for her. "Good?" he mumbled.

"Yeah," she replied, reaching back to squeeze his hand. Steve gave her a worried look, so she leaned over and kissed him. "I'm fine."

"Okay. Probably should get up and make this one something for breakfast, so she'll at least have something in her stomach before…"

"Before we give her all of the cotton candy and sugar she could ever eat," Darcy sighed. "Where did she even get Coney Island from?"

"Dunno - you were the one who was heading there when she showed up."

"If you had to spend a week working only nights, you would want to enjoy the sunshine too."

"But Coney Island? Place is a madhouse on holidays," he teased.

"I'm sorry Mr. 'I grew up in Brooklyn and all things touristy had lost their appeal' but some of us who grew up in the Midwest didn't know that it would be crazy down there."

"It's Coney Is - "

"Daddy," Emma groaned, her hand coming up to cover his mouth. "Too loud." Darcy snorted as Steve rolled his eyes fondly.

"Sorry baby."

"Are we going to Coney Island?" she asked, her head popping up.

"Uh… yes?" he said, glancing over at Darcy who raised an eyebrow. Emma turned to look at her as well with her sleepy blue eyes.

"Mommy?"

"If Daddy says so."

OOO

Emma was considered a high risk pregnancy because she'd been conceived with an IUD in place. For the first twenty weeks of her pregnancy Darcy had walked on eggshells, torn between the surety of the knowledge that Emma did exist and the fear that she could do something wrong to change that.

After the shock had worn off, Steve had been ecstatic. During the few hours they'd had Emma, the little girl had wrapped him around her tiny fingers. She'd batted her eyes at him until he took her on the rides and bought her whatever food her little heart desired - including two hot dogs, popcorn, cotton candy, and soda. Darcy had though it just desserts when she threw up on him after a rid on the kiddy roller coaster, though she'd felt bad as the little girl cried on her shoulder as Steve cleaned up.

The pregnancy had forced a few uncomfortable conversations.

Steve wanted to get married. Darcy did not.

Darcy wanted to continue traveling with Jane for as long as she could. Steve and the doctors did not.

Steve wanted her to move into the Tower. Darcy loved her tiny apartment in Red Hook and the distance from the craziness that was Manhattan her hour commute afforded her. Logically, she knew that it wasn't big enough but his assumption that his place was superior to hers when it was the target of the baddie of the week had irritated her. She would always blame the hormones for the accusations that she threw at him that day, like he was never there but trying to force her into some 1940s family ideal and prioritizing his career over hers.

Once tensions had finally lessened - which was aided by Steve's being out of the country for a week - they agreed to a sit down meeting to hash out their differences.

They would look for another apartment together. Darcy would talk to the doctors and Jane about going on every second or third trip until it became too dangerous for her to fly, and they would revisit the conversation as needed. Steve wouldn't push them getting married and he would make more of an effort to balance his responsibilities with the Avengers with their relationship.

OOO

"Pancakes!"

"Pancakes it is," Steve grinned as he threw Emma over his shoulder. The little girl shrieked with laughed and kicked her legs, which he pinned down as he neared Darcy. "Meet us downstairs when you're ready, Mom."

"Thanks," she said, tilting her head up to meet his kiss.

"My turn!" Emma demand, and Steve dutifully turned and crouched so that she was eye level with her mother.

"Morning baby. Make sure Dad saves me some bacon."

"No promises," Steve chuckled as he stood and let Emma drop a few more inches down his back so he held her by her knees. She laughed and clung to his shirt as they walked out of the room, leaving a smiling Darcy behind.

After a moment, she stood and collected the pile of dirty towels from their shower and Emma's quick bath to deposit in the laundry basket. The shower had helped her feel a bit more awake, but seeing Emma dressed in the same pair of jean shorts and little tank top they'd first seen her in had spiked her anxiety again. Even though they had a no shoes in the house rule, she'd had Emma put on her sandals just in case.

After changing into a pair of shorts and a loose t-shirt, Darcy started to made her way downstairs and chuckled at Steve's running commentary on breakfast preparations and his hiss of pain when the bacon popped.

"One panca - Emma?"

Darcy's heart was in her throat as she rounded the corner into the kitchen and saw Steve standing there, plate in hand, staring at the blank seat at the kitchen island. Emma's pink cup with orange juice and small silverware were set there, but no Emma.

"Steve?"

"She… she was just right there," he said, sounding dumbfounded. "Darce, she - "

"We have to let Jane know."

"Yeah...Jane." Darcy pulled her phone from her back pocket. "Shit," Steve grumbled when bacon grease splattered him.

"Swear jar," she said absentmindedly as she sent a text to her best friend, who quickly replied that she was on it.

OOO

She'd never believed in the nesting instinct until it hit hard just after Thanksgiving, a few weeks after they'd moved into their Brooklyn brownstone.

Steve had been indulgent as Darcy waddled around the house scrubbing at imagined cobwebs and sweeping for the fifth time. Annoyed that he hadn't put the baby furniture together and unable to do it herself (it was a struggle to get her own damn boots on some mornings), she'd called Thor who had thrown himself into the task enthusiastically. A bit ashamed, Steve called over Bucky to get the room painted.

Two days later, Darcy and Jane took a break from research and were talking to alleviate some of pelvic pain the former was feeling when her water broke.

In the early hours of December 10th, Darcy and Steve met Emma Grace Rogers for the second time.

When the new parents finally got home, they realized how much of a gift if was that Steve really only needed a few hours of sleep in order to be functional. Darcy, once again allowed to drink coffee, existed in a semi-catatonic state for the first few weeks until Emma started to sleep for stretches longer than three hours.

"Hey Darce?" Steve whispered one night as he burped Emma while Darcy adjusted the pads in her nursing tank top.

"Did she spit up?" she asked.

"No - at least I don't think so," he frowned, glancing at the cloth thrown over his shoulder.

"Ok. I'm going to go pee and then I can change her so - "

"Darce?"

"Huh?"

Steve smiled at her, taking in the hair piled up on the top of her head and the glasses sliding down her nose. "Will you marry me?"

OOO

"She's gonna be okay, right?" Darcy asked as Steve slid a plate piled with pancakes and bacon across the island towards her.

"She's going to be fine," he assured her before picking up a strip of bacon. "She's going to eat too much junk and have fun at the beach."

"Steeeveee," Darcy groaned, pushing away her plate to rest her head on the cool granite countertop. "She's going to get sick. What if she was scared but just didn't tell us? We don't exactly look like we did back then."

"You said you liked the beard," he sighed, moving around the counter to stand in front of her. Darcy huffed and leaned into him, wrapping her arms around his waist.

"I do, but you didn't have it back then."

"And if she gets scared, then we'll take care of it. I'm kind of great at doing that."

Darcy shook her head and groaned. "She's gonna be confused. You didn't even know who I was - "

"Did too." When she cocked an eyebrow at him, he shrugged. "What? I knew who you were, I was just being a gentleman."

"Right."

"How could I not? You were all curves and lips," Steve smirked before leaning in to kiss her. "And the cursing! Oh, the cursing! Do you know how bad it would have looked if everyone knew Captain America was turned on by some bad language?"

"Oh the scandal."

Steve chuckled and pressed a kiss into her hair before pulling back. "Let's just pretend that Buck took Emma for the day so we could spend some time on my birthday alone." Darcy groaned and brought her hands up to her face. "What's wrong?"

"I forgot to get you a birthday present."

OOO

"Okay, this should work," Jane said.

"You're sure?" Darcy asked as she glanced up at Steve, who turned to look at the little girl Bucky was holding.

"I mean, it's theoretical - time travel wasn't really a thing until today, Darcy!" Jane snapped, her voice getting louder and squeakier towards the end.

"What she's trying to say," Tony sighed, stepping between the two women. "Is that we've stabilized this enough to get her back but it's a one way trip."

"So you're saying we can't go with her? Make sure she gets back?" Steve frowned.

"Don't trust us, Rogers?" Tony smirked.

"Tony," Bruce sighed, a hand over his face. Bucky's eyes flashed dangerously. "She's their daughter."

"Have you even tested this thing, Jane?" Darcy, holding out an arm to stop Steve when took a step forward. A flush crept up her cheeks - it'd been relatively easy to ignore the fact that Emma was their daughter and everything that implied when they'd been away from the Avengers and Co. but it had been non stop teasing and innuendo since they'd gotten back to the Tower.

"On small organic matter - "

"Fruit," Bruce grumbled. Steve felt a bolt of fear go through him and motioned for Bucky to hand over the little girl, who had left a sizable drool spot on his t-shirt. Buck wrinkled his nose as Steve held her tightly, drawing comfort from her solid weight.

"But it should be fine. It's a similar design to the mobilized teleportation spikes that Erik used during the Convergence. It'll still be working with the - "

Darcy sighed. "Short version for the non-scientists."

"Basically I've made his tech travel forward rather than sideways," she huffed. "Bruce somehow got it to lock onto DNA matches and Tony miniaturized it so that all Emma has to do is push the button and - if this is calibrated right - it'll take her back to the same day she disappeared from."

Steve looked at Darcy, trusting her judgement with Jane's work. She sighed and closed her eyes for a long moment before groaning. "If you're sure…"

"I am, Darce - I wouldn't even suggest it if I didn't think it would work," Jane said, her eyes darting from Darcy to the little girl.

"Fine. Show me what she needs to do."

Steve walked away from the group towards a quiet corner of the lab and sat on one of the stools, shifting Emma so that her head was curled in the crook of his neck. "Sweetheart," he said, gently shaking her. "You need to wake up now."

"Nooo," she groaned, her hand curling in the collar of his shirt. Steve felt his heart in his throat as his eyes traced her face, trying to memorize the smallest details.

"Come on," he chuckled, bouncing his leg until she laughed and opened her bleary eyes. "Mom's gonna be here in a minute and we need you to do something for us."

"Do I have ta?"

"Yup, you have to. But then you can go back to sleep - promise."

"Okay. Did you have a good birthday, Daddy?"

"The best," Steve answered quickly, pulling the little girl closer as Darcy walked towards them. He watched as she took a deep breath and pasted on a smile that didn't quite reach her eyes.

"Alright, Munchkin! Time to head home. You ready?" Emma nodded and held her arms out to Darcy, who smiled and quickly settled the girl on her hip. "Okay, but we're going to go home a special way this time. Auntie Jane, Uncle Tony, and Uncle Bruce made this special for us to get back to the house faster - all we need to do is touch this," she held out her palm to reveal a small button on a wristband small enough for Emma, "and think about home. Think we can do that?"

"Mmmhmm," Emma nodded, reaching for it. Darcy quickly transferred the girl to the floor and crouched down beside her to put the bracelet on her.

"So what are we doing?" Darcy asked.

"Push this and think of home," Emma parroted before her looking up at her mother through her eyelashes. "Are we gonna have cake 'n ice cream when we get home?"

Darcy laughed and blinked away the tears in her eyes as she pulled the girl close enough to press a kiss into her hair. "I think you've had enough sugar for today, Sweetie."

"Are you sad, Mommy?" Emma frowned.

"Just tired," Darcy said, shaking her head. "It's been a loooong day."

"Maybe Daddy will tuck you in when we get home," Emma grinned. Across the lab, Bucky hastily turned a laugh into a cough when Steve shot him a look.

"Alright troublemaker - give your… your Dad a hug." Steve didn't waste a moment but scooped her up and held Emma tightly before turning to kiss her cheek.

"Too tight, Daddy!" she protested, squirming in his arms.

"Sorry," he said while loosening his grip. "Be good, okay?"

"You're coming home too," Emma frowned. "You're not going away again." Steve looked over her head at Darcy, who shrugged.

"Nope, not going away again. Just going to be a little bit behind you and Dar - Mom."

"Okay. I love you, Daddy."

"Love you too, honey," he whispered around the lump in his throat as he set her on her feet.

Darcy leaned forward to hug her again and Emma whispered loudly in her ear, "I'll love you more than Daddy if I can have cake."

"Guess you're just gonna have to love him more than me," she laughed, glancing up at Steve. Emma sighed and crossed her arms, sticking her lower lip out. "I don't negotiate with terrorists."

After going over the instructions one more time, Darcy sat back on her heels while Emma held up her wrist. Her eyes darted from the button to her mother before a smile spread across her mouth. "I love you, Mommy."

"Love you too, baby," Darcy said before Emma pressed the button and disappeared.

It was silent in the lab as everyone looked at where the little girl had been moments before. But then Steve moved and held out a hand to Darcy to help her up. "You think she's okay?" he asked.

"I hope so."

"That was…"

"Yeah…"

"Did you maybe want to grab a coffee sometime?"

"Maybe," Darcy said. "But I would really love a stiff drink right now."

OOO

Oddly enough, it had been reassuring when fruit had started appearing in the kitchen throughout the day, even though cleaning up the watermelon that had fallen off the barstool hadn't been fun. After the first fruit appearance - a handful of blueberries - Jane had managed to text Darcy at least a minute before the next round's appearance to let her know there was incoming; apparently there were enough fluctuations over the brownstone to trigger her equipment.

Emma reappeared at 6:59 PM - one minute before bedtime - much to her parent's relief. Darcy had quickly scooped her up and peppered her face with kisses before Steve gently moved them upstairs to get her ready for bed.

"So I know what I want for my birthday," he said as they sat on the couch later that night with Emma safely upstairs in her room, sleeping off the sugar high their past selves had inflicted on her.

"Hmm," Darcy asked, lifting her head from where it had been resting on his shoulder. Her eyes struggled to focus on his, and a smile tugged at the corner of his mouth as he brushed a strand of hair from her face before his hand fell to down her hip.

"Will you finally marry me before this one comes?" he asked, his thumb tracing the gentle curve of her stomach.

* * *

**Author's Note:** My friend (Ao3 name Penelope_in_Wait) gave me the exchange where Steve says he knew her. Posted this chapter today and I'm officially done with this story which was supposed to be a one shot. Hope you enjoyed it!


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